But if you want to know how to Venmo like a millennial, it’s all about the “penny poke,.”

Penny pokes are tiny charges, mere cents, that are sent to gratitude for a friend, say hello or get the attention of a celebrity. The act of penny poking refers to sending any payment that is less than $1.

While penny poking may sound silly, it’s incredibly common. Venmo’s team reviewed public transactions on the app over the past year and found there were 3.8 million penny pokes sent on the app.

Venmo users are also throwing coins–virtually, of course– at celebrities, whether to get their attention or to simply “buy” them a drink.

One diehard Chicago Bears fan went beyond the usual penny poke and used the app to send quarterback Mitchell Trubisky $8 for a beer every time the team won. Becca Kufrin, who was dumped by “The Bachelor” star Arie Luyendyk Jr. received more than $6,000 in Venmo penny pokes last year after she was blindsided and dumped on TV. Kufrin said she donated the money to charity.

Even John Graham, one the app’s first employees and also known as “Venmo John,” received his share of penny pokes from fans after he was sent home on Kufrin’s season of “The Bachelorette.”

Of course, fans kept with the cheeky theme and sent the engineer two cents as a symbolic gesture.

Because of Venmo’s various fees, it’s difficult to say how much the payment service earns from penny pokes. Venmo charges a 3% fee when money is sent using a credit card. The company also takes a 1% cut when someone chooses an “instant transfer” of their balance to their bank account. So while it may some money from this trend, but in terms of big corporate revenue streams, it’s more like pocket change.